The present invention relates generally to a reference voltage generating circuit. More particularly, the invention relates to a reference voltage generating circuit having improved output voltage stability.
Many circuits and components within semiconductor devices require one or more reference voltages as part of their various control inputs. Accordingly, conventional semiconductor devices often include specific circuits providing uniform reference voltages. So-called reference voltage generating circuits generally provide a reference voltage (Vref) from an external power source voltage (VDD). For stability and reliability in the operation of the constituent semiconductor device, reference voltage generating circuits should output a fixed reference voltage regardless of variations in the operating temperature of the semiconductor device and/or the level of noise apparent on related signal lines and input/output points.
This simple requirement, however, can prove difficult to implement. This is particularly true where the level of the applied external power source voltage varies due to uncontrolled environmental factors, such as temperature. Fluctuations in the external power source voltage often cause instability in the reference voltage output provided by conventional reference voltage generating circuits. Such instability in the generation of one or more reference voltages can adversely affect the reliability and stability of the semiconductor device.